Relay device



July 23, 1968 RELAY DEVI CE H. R. JAQUITH Filed Oct. 11. 1965 Fig. 4

HOWARD R. JAQUI TH INVENTOR.

United States Patent O 3,393,705 RELAY DEVICE Howard R. .laquith,Rochester, N.Y., assignor to Taylor Instrument Companies, Rochester,N.Y., a corporation of New York Filed Oct. 11, 1965, Ser. No. 494,848 8Claims. (Cl. 137-6256) ABSTRACT OF THE DISCLOSURE One side of a firstpiston is connected to one side of a second piston by a stem, and theeffective area of the first piston is larger than that of the secondpiston. A body provides corresponding bores for said pistons, saidpistons and bores being coaxially arranged. A pilot valve means providesfor connecting bore space between the pistons to bore space on the otherside of the larger piston, or for sealing of one said space from theother, and exhausting the latter space to atmosphere. A fluid pressuremotor and a fluid pressure source also communicate with thebetween-piston space. When the pivot valve disconnects the said spaces,the net force on the pistons drives the larger piston into its space,which results in the smaller piston moving to a position where it isbetween the connections of motor and pressure source, the latter beinglocated such as now to be on the other side of said smaller piston,whose bore opens into atmosphere at said other side. When the pilotvalve connects the first said spaces, the pressure source acts on bothsides of the larger piston. The said one side of said larger piston isdiminished in effective area by the stern, and the pressure on the otherside of said larger piston forces it outwardly of its bore space, movingthe smaller piston to a place where the motor now connects to thebetween-piston space and therefore with the fluid pressure source.

This invention relates to relay devices such as the valve disclosed inUS. Letters Patent N0. 2,261,287 to William J. Brown and Evan A.Edwards, dated Nov. 4, 1941.

One object of the invention is to provide a new and improved relaydevice for controlling the connections between a pressure fluidutilization means and various pressure fluids.

Another object of the invention is to provide a new and improved relaydevice wherein the said device is actuated by force due to pressurefluid and said pressure fluid also provides the bias needed to createsaid force.

It is also an object of this invention to provide a new and improvedform of construction for such relay device, wherein such construction ischaracterized by economy, simplicity, ease of manufacture, efliciencyand reliability.

These and other objects of the invention will be apparent from thedetailed description to follow and from the claims appended hereto.

Briefly, a relay device according to the invention consists essentiallyof a simple casing, incorporates a pair of pressure-movable walls, andhas a simple pilot valve externally operated for controllingdistribution of pressure fluid to said walls. One of said walls has alarger effective area than the other, the said other thereof providesvalve means for connecting pressure fluid to utilization means, and bothare connected together to move as a unit. The said casing has but fewexternal connections to sources of pressure fluid and but two pressurefluid seals between it and said walls.

In the drawing, FIGURE 1 is a partly sectional view of a relay device inaccordance with the invention; FIG- URE 2 is a sketch showing the relaydevice according to the invention in an aspect of its operation notshown in FIGURE 1; FIGURE 3 is a sketch of a modified form of relaydevice in accordance with the invention; FIG- URE 4 is a partlysectional view of a relay device in accordance with the sketch of FIGURE3; FIGURE 5 is an end-view of the device of FIGURE 4.

In FIGURE 1, reference numeral 1 generally denotes a relay deviceaccording to the invention. The use of this kind of device is typicallyto connect a source 2 of air under pressure with a bellows 3, or otherpressure fluid operated device, in order to cause the bellows to expandand in so doing, to do work in proportion to the dilfen ence between thepressure inside the bellows and the pressure outside the bellows. Thus,we may suppose the lefthand end of the bellows to be fixed to someimmovable place 4 and to expand toward another immovable place 5,overcoming resistance to such expansion, such resist ance beingsymbolized as a spring 6, interposed bewteen place 5 and the right-handend of the bellows so that if bellows 3 expands, the spring iscompressed. For example, bellows 3, places 4 and 5, and spring 6 areanalogous to the valve V of the Brown and Edwards patent, identifiedabove, operation of which requires that the valve-actuating pressure dowork to overcome various resistances, such as friction, springs,pressures, etc., in operating the valve.

At other times, it is desired to release to atmosphere the air frombellows 3, so that the bellows contracts, whereby work is againperformed as a result of releasing the force stored up in spring 6.

Relay device 1 comprises a pilot valve block 7 and a control valve block8. Block 7 has passages 9, 10 and 11 therein. Passage 9 opens at thesurface of the block 7 at one end, and terminates inside the block 7with its other end opening into One end of passage 10, which is entirelywithin the block. (Normally, passage 10 would be formed by drillingthrough one side of the block and closing the opening in the sidethereafter.) Passage 10 opens at its other end into a passage 11 whichopens at one end in the lower face of block 7, and at its other endopens into the bottom of a counterbore 12 opening at the upper face ofblock 7.

Passage 11 has a movable stem 13 therein which terminates at its end inrespective valve plugs 14 and 15, said plugs being formed tosubstantially seal the ends of passage 10 when one or the other isseated in one of said ends. Conveniently, the passage 11 iscyclindrical, and the block surfaces surrounding its ends are flat. Theplugs are then provided in the for-m of spheres of greater diameter thanthe passage 10, whereby when a plug is seated in an end of passage 10,the plug will substantially completely close off the passage 10 at theend in which it is seated. Also, the stem may have one of its endsthreaded (not shown) so that the corresponding plug may be removablysecured thereto by means of a tapped hole therein (not shown) into whichthe threaded end of the stem 13 is screwed, and thereby allowing thestem 13 and plugs 14 and 15 to be assembled to block 7 in the mannerillus trated. Since the main function of the stem 13 is to cause theplugs 14 and 15 to move substantially in unison, it need not necessarilybe attached thereto. In such case, it would be necessary to providesuitable means for guiding plug 14 into and out of seating position.

Control valve block 8 has passages 16 through 21 therein. One end ofpassage 16 opens into the bottom of a counterbore 22 opening at thelower surface of block 8, and the other end of passage 16 opens into oneend of a passage 17, the other end of which opens into the side ofpassage 18. Passage 18 runs downward from the top surface of block 8,merging inside block 8 with a larger diameter passage 19 whose other endopens at the lower surface of block 8, to define one overall passageextending vertically through the block 8.

A passage 20, which may be a continuation of passage 17, opens into oneside of passage 18, as does a passage 21. Respective pipes 22 and 23 areconnected to passage 18 via passages and 21, to provide for transfer ofair to and from the source 2 and to and from the interior of bellows 3.Pipes 22 and 23 may, of course, be much longer than indicated in thefigure.

The blocks 7 and 8 are mated together at the top surface of the formerand the bottom surface of the latter, a gasket 24 being providedtherebetween so that when the screws or similar means (not shown) usedfor fixing the blocks together are applied, an hermetic seal between themating surfaces of the blocks results.

Counterbores 12 and 22 are so located that their openings coincide witheach other so as to define a chamber permitting sufiicient freedom ofmotion for plug 15 to allow seating of plug 14 in the lower end ofpassage 11. Passage 19 is so located that the passage 9 registers with,i.e., opens into the opening made in block 8 by passage 19. Gasket 24is, of course, perforated to provide holes matching the openings ofcounterbore 22 and passage 19.

Passages 18 and 19 provide the bore of a cylinder having therein aplunger or piston unit 25, which is designed for reciprocation alongsuch bore in the general fashion of a piston. Piston unit includes apiston 26 and a piston 27 integrally connected together by means of astem 28, and respectively sealed by O-rings 29 and to the inner walls ofpassages 18 and 19, so that though the pistons slide along theirrespective passages and need not have a close fit thereto, the O-ringssubstantially prevent leakage of air past the pistons.

As shown in the drawing, piston 27 is as far up as the verticaldimension of passage 19 will allow it to go, and plug 14 is representedas seating in the lower end of passage 11. As the spacing betweenpistons 26 and 27 is such that passages 17, 20 and 21 open into theannular space in bore 18 surrounding the portion of stem 28 be tweenpistons 26 and 27, and since the plug 15 is clear of upper end ofpassage 11, therefore air from source 2 pervades all the describedpassages in the blocks 7 and 8, save for a small portion of passage 18above piston 26.

By way of example, source 2 may be considered to be a compressor, or thelike, adapted to supply air under a pressure of 20 p.s.i.g. (pounds persquare inch over atmospheric pressure), or more, to a volume such as thesaid passages, piping 22 and 23, and the interior of bellows 3 provide,and to maintain that pressure in said volume despite a certain amount ofleakage therefrom, occasional exhausting of that volume to a lowerpressure region such as the atmosphere, and/ or air consumption by theutilization device connected to passage 21. As the relay device 1 isnormally located in the atmosphere, it is evident that piston unit 25 isbiased into the position shown in FIGURE 1 by a force equal to theeffective area of piston 26 times the difference between atmosphericpressure and the pressure of the air supplied by source 2, the saideffective area being substantially that of the cross section of passage18 which, for convenience, along with passage 19, may be considered tobe circularly cylindrical in form with FIGURE 1 therefore representing adiametral cross-section on the common axis of passages 18 and 19.

Taking the pressure external to bellows 3 to be atmospheric, it will beevident that the bellows 3 will be extended a certain amount (dependingon the strength of spring 6 and other resistance, if any) by a forceequal to the effective area of bellows 3 times the difference betweenthe pressure of the air therein and the atmosphere.

If plug 15, however, is caused to seat in the upper end of passage 11,so that the plug 14 is moved out of the lower end of passage 11, the airin the portion of passage 19 beneath piston 27, and in passage 10 andpassage 11 will escape to atmosphere, and atmospheric pressure willreign in this region. Consequently, the net force on piston unit 28 willbe reversed, for the net force tending to hold it in the position shownin FIGURE 1 is equal to atmospheric pressure, and the net force tendingto move it out of the last said position will be equal to the differencein effective areas of the pistons 26 and 27 times the pressure of theair supplied by source 2. In fact, by choosing the diameters of thepassages 18 and 19 such that the crosssectional area of the latter istwice that of the former, the magnitude of the net force acting on unit28 will be the same no matter which of plugs 14 and 15 is seated in thecorresponding end of passage 11. However, the direction of this forcewill be toward the open end of passage 18 if plug 14 is seated, buttoward block 7 if, instead, the plug 15 is seated. Due to the sealsprovided by O-rings 29 and 3'0, the effective areas of the pistons arethe same as the cross-sectional areas of the respective passagescontaining the pistons.

When the plug 15 is seated, the resultant net force pushes piston 27 asfar toward block 7 as it can go (it is desirable to provide someirregularity on the surface of the bottom of piston 27, or likeexpedient, to prevent the piston 27 from fitting too closely to, or tokeep it just out of contact with the upper block of block 7), i.e.,substantially all the way to the top of block 7, the location of theopenings of passages 17, 26 and 21 in passage 18, and the spacingbetween pistons 26 and 27 are such that the O-ring 29 passes over theopening of passage 21 into passage 18, and attains a position in passage18 where it prevents transfer of air between passages 20 and 21 viapassage 18. Consequently, the passage 21 now opens into that part ofpassage 18 above piston 27 that is open to the atmosphere, and the airinside bellows 3 now vents to atmosphere and the spring 6 releases theenergy stored in it and compresses the bellows. Passages 17 and 20,however, remain in communication with each other via the annular spacearound that part of stem 28 that lies between pistons 26 and 27.

Since in practice it is found that a pressure of 5 p.s.i.g. from source2 is enough to move piston unit 25 in one direction or the other, inspite of O-ring friction, inertia effects, or the like, and since as arule the usual source 2 is more likely to be capable of providingpressure at p.s.i.g. than even 20 p.s.i.g., therefore the action ofpiston unit 25 can be quite powerful and quite positive, even though thedimensions of the relay device be relatively small. (Save for minoridiosyncracies of form, that would result from machining the blocks 7and 8 to produce the various passages, FIGURE 1 follows manufacturingdimensions closely but is about twice as large as life.)

It will also be observed that the tolerances involved in making therelay device are quite liberal in general. Thus, pistons 26 and 27 needfit their respective passages no more closely than necessary to obviatethe possibility of the O-rings 29 and 30 being extruded between thepistons and the passage walls by such pressure drops as may obtainacross the O-rings, in use of the relay device.

In practice, the O-rings 29 and 30, the respective annular grooves 26aand 27a receiving said O-rings, and bores 18 and 19, are so dimensionedas to provide what is known in the prior art as floating O-ring sealsfor pistons 26 and 27. The opening of passage 21 into passage 18, i.e.,the intersection of the cylindrical surfaces defined by those passages,is deburred, and both O-ring 29 and O-ring 39 are lightly lubricated. Asa result, piston unit 25 is capable of millions of cycles of smooth,relatively friction-free movement despite the rub-hing of the O-rings onmetal surfaces and the passing of O-ring 29 across the opening ofpassage 21 into passage 18, and without maintenance other than anoccasional renewal of the lubrication of O-rings 29 and 30.

The lower surface of block 8 and the upper surface of block 7 must besufiiciently smooth and mate well enough together that the gasket 24 canseal these surfaces together. The plugs 14- and 15, moreover, and theends of passage 11 should be finished relatively accurately andsmoothly, since the valving action here involves a metal to metalcontact. It should be noted, however, that insofar as operation isconcerned, the minimum pressure needed for operation can be so smallcompared to that usually available that leakage is of no moment providedthat the pressure in bellows 3 can be raised to a high enough level forit to do the work demanded and provided that wasting the capacity ofsource 2, in leaking air, is not objectionable. Routine drilling andfinishing operations, however, suflice to provide a substantiallyleakless structure in which substantially no air is consumed except theair lost by exhausting the portion bore 19 below piston 27, for thepurpose of moving the piston unit 25 down to where piston 27 bottoms atthe lower end of passage 19, and the air transferred to the bellows 3.

Since the force on piston unit 25, due to pressure, reverses wheneverthe pilot valve in block 7 is actuated as described, no biasing spring(such as spring 17 of the above-identified Brown and Evans patent) isrequired.

For operating the pilot valve, there may be provided a lever 31 pivotedat 32 (say, a part of block 7, in effect). As shown, lever 31, whichwould be more or less rigid, has a spring blade 33 fixed by one end tolever 31 near pivot 32. A reverse bent end 34 of lever end provides aseat for the free end of spring which is arranged so that it would pressagainst said end 34 save for a member 35, represented as deflectingblade 33 upward. The stiffness and initial position of spring 33 arechosen such as to provide an initial force which is a little more thanis required to prevent it from bending if sufficient force is appliedthereto so as to deflect lever 31 upward and cause plug 14 to seat inthe end of passage 11 and to stay seated. The force tending to unseatthe plug 14: its weight (and that of plug and stem 13) and the pressuredrop thereacross when seated, is small. Insofar as the influence ofweight is concerned, this is sutliciently slight that the operation ofthe relay device is unatfected by its orientation.

Member 35 represents part of an entity capable of moving member 35farther than is necessary, or possible, to move the plug 14, withoutsome inconvenience or even damage to such entity or to the relay, unlessthe excess motion is somehow accommodated. As shown, spring 33 absorbsexcess motion of member 35, as it can deflect safely and withoutconsequence for a considerable distance.

It is easy to see from the foregoing that once member 35 retreats farenough from blade 33, the pressure drop across plug 14 unseats it(gravity aids also, if vertical in the drawing is taken to represent thevertical in practice) about as quickly as the retreat of member 335permits, and plug 15 seats very shortly thereafter, thus sending pistonunit 25 down.

From the description herein, it is evident that piston 26 and O-ring 29represent a movable wall responsive to pressure and, as well, a valveacting as means for connecting bellows 3 to either one of two sources ofpressure fluid, namely, the atmosphere and source 2.

Considering that the relay device has four passages or connections viawhich pressure or pressure fluid can be applied to it and/ or admittedto it, it is evident that there are other possibilities in the way ofpressure and pressure fluid sources with which the relay device may beused. Thus, source 2 may be an evacuating device, i.e., a source of airat say about 9-10 p.s.i. absolute pressure or less (i.e., a pressurethat is less than atmospheric by 5 p.s.i. or more). In this instance,piston unit 25 would be in the position shown in FIGURE 1, but with theplug 15 seated and the plug 14 unseated as in FIGURE 2, whereas with theplugs positioned as shown in FIGURE 2, the piston unit 25 instead wouldbe in the position shown in FIG- URE 1.

Again, passages 11 and 18 need not connect to atmosphere (i.e.,approximately 15 p.s.i. absolute) but to a source that provides air at 5or more p.s.i. different in pressure level from the air of source 2.Again, as the pressure external to bellows 3 is mainly significantinsofar as it enters into determining how much bellows 3 expands andcontracts, whereas it does not influence the force on piston unit 25, itcan be of a magnitude unlike that of any of the other pressures.

The foregoing applies particularly to elastic fluids. In the case ofinelastic fluids (i.e., liquids), it is only inapplicable to the extentthat the incompressibility and liquid head effects must be taken intoaccount. However, if source 2 is the type of source such as is usuallyadopted for hydraulic servo systems wherein discharge from the passages11 and 18 is to the usual sump from which hydraulic liquid isrecirculated by the source to the relay device, the said effects wouldbe only of minor significance and would not influence the basic designof relay device appreciably, or in any Way that would not be obvious toone skilled in the art.

As a pratical matter, the structural form indicated by FIGURE 1 is to bepreferred. Moreover, the dual role of piston 26 rather requires it to besuch, as opposed to a diaphragm or bellows which, though each of theselast is rather piston-like, in many respects, could not very wellperform the same valve action, since it would have a peripheral portionsealingly fixed in place. The piston 27, on the other hand, could bereplaced by a diaphragm or bellows as no valve action is involved.

Again, the pilot valve defined by plugs 12 and 14 and stem 13, is butone of several known types capable of performing the same function (asis also the case with the pilot valve operating mechanism includinglever 13), and utilization devices other than bellows 3, etc., could beoperated by relay device 1. It is also evident that the various passagescould be provided in the form of tubular pipes, cylindrical casings, andthe like, of relatively thinwalled nature, as compared to the relativelymassive blocks 7 and 8, in which the necessary passages are provided bydrilling cylindrical holes therein.

Nevertheless, it will be observed that the specific relay deviceillustrated consists in FIGURE 1 essentially of but two moving parts,namely, piston unit 25 and the pilot valve consisting of stem 13 andplugs 14 and 15, in a monolithic stationary part, and each of said partsis in itself composed of few separate parts. Thus, the piston unit 25need consist of but a sing-1e cylindrical element machined out of acylindrical bar, (plus O-rings, of course).

FIGURE 3 shows a form of the invention wherein the relay device providesfor swtching between the pressure of source 2 and the pressure of anadditional pressure source 102, and wherein the switching is controlledby a third pressure source 202. As will be seen by comparison withFIGURE 2, the only basic structural distinctions involved are to closeoff, in effect, passage 17, to provide a connection 36 between the upperend of chamber 18 and source 102, and to provide a connection betweenthe source 202 and the passage 16.

In this form of the invention, the pressure of source 202 must begreater than the sum of the pressure of source 2 and the differencebetween pressures of sources 2 and 102 times the ratio of the effectivearea of piston 25 to the effective area of piston 27. Likewise, the saidsum must be greater than the pressure acting on the piston 27 viapassage 9 when the ball 15 cuts off the pressure from source 202 (thecondition illustrated by FIGURE 3). In each case, the excess must besuflicient, of course, to overcome O-ring friction, etc.

On the other hand, if the pressure acting on piston 27 via port 9 isatmospheric, then the pressure of source 2 could be atmospheric, that ofsource 102 could be infraatrnospheric, and that of source 202 could be afew p.s.i. larger than the sum of the former. Again, all three of thesepressures could be much larger than atmospheric pressure.

More generally, the following inequality governs:

A =Etfective area of piston 26 A =Effective area of piston 27 P Pressureof source 102 (or in the open end of chamber 18, FIGURE 1) P Pressure ofsource 2 xP Pressure of source 262 expressed as a fraction as (proper orimproper) times P (since, of course, pressures of substantially fixed,known values are involved) F=Force necessary to overcome resistance ofpiston assembly to moving (O-ring friction, etc.)

The inequality, supra, applies to FIGURE 1, i.e., then x=1 and P=ambient atmospheric pressure, and to FIGURE 3, i.e., xP =P the pressureof source 262.

It will be evident from the foregoing that the sole functionaldistinction of any structural consequence between the relay device ofFIGURES 1 and 2 and the modification of FIGURE 3 is the provision in thelatter of the two separate sources 2 and 262 of pressure for piston 27,one for each side, instead of allowing the one source 2 to act on bothsides. This is due to the fact that conduit 17 is closed or eliminated.Optionally, FIGURE 3 may, for convenience, involve other structuralmodifications, such as closing the open end of chamber 1% and providingfor connecting passage 36 through the side of block 8 in line withconnections 22 and 23. Likewise, the block '7 may be replaced by asimple closure plate, and passage 9 shifted around to the side of block8, so to speak, into alinement with passages 21? and 21, the pilot valvein block '7 being provided as a structural unit distinct from the relaydevice proper. These alterations would provide for manifolding all thepressure connections to the relay device, and remote location of thepilot valve, but would not bring about any change in the principles ofoperation as set forth in connection with the description of FIG- URES1, 2 and 3.

In illustration of the foregoing, the relay device of FIG- URE 3 may berealized as in FIGURE 4- wherein reference numeral 108 denotes a blockthat is substantially the counterpart of block 8, FIGURE 1, and ingeneral each FIGURE 4 counterpart of an element of FIGURE 1 has areference numeral that is that of said element plus 100. Thus O-rings129 and 130 correspond to O-rings 29 and 30, and so on. It may be notedthat stem 126 is in effect piston 26 and stem 25 combined, that piston129 and stem 126 fit somewhat loosely (D-rings are relied on for sealingpurposes, however, in both FIGURE 1 and FIG- URE 4), passage 136 isactually the counterpart of connection 36 of FIGURE 3, and whatcorresponds to the open end of passage 18, FIGURE 1, is closed by asphere 37 or other plug, force-fitted into the open end of passage 118.Such distinctions as these are of no functional significanee.

However, in accordance with the scheme of FIGURE 3, passage 17 isomitted. Moreover, the block 7 is replaced by a simple closure plate 38(sealed to the block 108 by a gasket 124) in place of a valve-containingblocklike block 7, thus eliminating the equivalent of passage 16 fromthe relay device proper. Block 108 has a projection 38 thereonillustrating a suitable way of keeping the piston 127 from seating itsflat end surface totally on the otherwise flat plate 38. It will also beevident that the inner end of passage 119 is conical, hence the flatannular inner end surface of piston 129 cannot seat thereonsubstantially.

The passages 109', 12ft, 121 and 136 are alined with each so as to openout on one side (preferably flat) of the block and continue on into amanifold 4% through a suitable gasket 41 sealing the manifold 45 to theblock 108. The last said passages open into tapped holes 42 through 4-5provided in manifold 419 for the purpose of connecting to the entitiesshown in FIGURE 3. Thus, a pilot valve would connect to tap 42, as onedoes to the passage 9, pressure sources 2 and 192- would connect to tap43 and 45, respectively, and a bellows or the like would connect to thetap 44. Suitable means (not shown) are provided to maintain manifoldat), block 108 and plate 38 in the assembled relation illustrated.

FIGURE 5 is an end view of the relay device of FIG- URE 4, internalparts nearest the point of view being shown in broken line.

The operation of the relay device shown in FIGURES 4 and 5 is, ofcourse, as described in connection with FIGURE 3.

In accordance with the statutes, I have described my invention withreference to the best embodiment thereof known to me thus far, and insuch terms as to enable one of ordinary skill in the art to make and useit. Having done so, I wish to make it clear that the scope of myinvention is to be determined with reference to the claims appendedhereto, rather than by the detailed description herein of the invention.

I claim:

1. A relay device including a first wall and a second Wall, said wallsbeing connected together for motion, as a unit, along a given path, theeffective areas of said walls being transverse to and spaced along saidgiven path, so that one side of said first wall faces one side of saidsecond Wall, and the effective area of said first wall. being largerthan that of said second wall; first means for simultaneously providingsaid one side of said first wall and said one side of said second wallwith first pressure fluid, said first means providing a space betweensaid one side, said space being shaped and dimensioned such as to permiteach said wall to move freely into said space without changing theeffective area of said one side; second means for providing the otherside of said first wall with second pressure fluid, third means forproviding the other side of said second wall with third pressure fluid;and fourth means for connecting pressure fluid to utilization means whensaid fourth means is connected to such pressure fluid; pilot meansoperable to provide said other side of said first wall with pressurefluid of sufficient magnitude that the force due to pressure on saidother side of said first wall is greater than the force due to pressureon said one side of said first wall plus the force due to pressure onsaid other side of said second wall and minus the force due to pressureon said one side of said second wall, so as to move said walls from afirst position on said given path to a second position thereon; saidsecond wall defining valve means operative when said walls are in saidsecond position to connect said first pressure fluid to said fourthmeans, whereas when said walls are in said first position said valvemeans is operative to connect said third pressure fluid to said fourthmeans.

2. The relay device of claim 1, wherein said pilot means, when operated,is constructed and arranged to supply said first pressure fluid to saidone side of said second wall.

3. The relay device of claim 1, wherein said valve means includes afirst passage and a member therein sealingly and slidingly received bysaid passage for movement therealong, second and third passages openingint-0 said first passage and being spaced along the path of movement ofsaid member, said path of movement being from a position of said memberbetween the openings into said first passage of the said second andthird passages to a position thereof beyond said openings and with theopening of said third passage being between said member and the openingof said second passage, said member constituting said second wall, andsaid fourth means including said third passage, and said first meansincluding said second passage.

4. The relay device of claim 3, wherein said first wall is a memberslidingly and sealingly received in said first passage and in a portionof said first passage extending on the other side of the opening of saidsecond passage from said third passage.

5. The relay device of claim 1, wherein said pilot means is a pair ofplugs connected by a stem, and there being a part having a passagetherein opening at each end at a surface of the part, said stem beingreceived loosely in said part and being of sufficient length that bothof said plugs are outside the last said passage, and the said plugsbeing so dimensioned and shaped as to 'be able to seal the ends of saidlast said passage if seated therein, said part having a further passagetherein opening at one end into the said last said passage thereinintermediate the ends thereof, said first means being connected to oneend of said last said passage, said second means being connected to theother end of said last said passage, and said further passage meanshaving its other end arranged to provide pressure fluid to said otherside of said first wall.

6. A relay device including a block, said block including four openingsat one external surface area thereof, there being a bore in said blockconnected by first passage means at one end thereof to one of saidopenings, a pressure responsive first wall closing said bore and movabletherealong, second passage means connecting a second of said openingsand opening into said bore at a place Where said first wall is betweensaid place and said one of said openings, a pressure responsive secondWall closing said bore and movable therealong and so located that saidplace is between said first wall and said second wall, third passagemeans opening into said bore between said second passage means and saidsecond wall; fourth passage means opening into said bore on the otherside of said second wall from said first wall, said third passageconnecting a third of said openings with said bore and said fourthpassage means connecting a fourth of said openings with said bore; theopenings into said bore of said second and third passage means being solocated along the line of movement of said second wall that said secondWall is between the last said openings at one position in its path ofmovement, and at another position in its said path of movement saidsecond wall is between the openings into said bore of said third andfourth passage means; said second wall being in the form of a pistonslidingly sealingly received in said bore and having a lesser effectivearea than said first wall; both said walls being effectively rigidlyconnected together with respect to line of movement of said second wall.

7. The relay device of claim 6, wherein said first wall is also in theform of a piston slidingly sealingly received in said bore.

8. The relay device of claim 6, including a manifold plate sealed tosaid one surface area, said plate having four tapped openingscorresponding to the first said four openings and in registry therewith.

References Cited UNITED STATES PATENTS 663,727 12/1900 Chris-tie et a1137-6256 2,617,444 11/ 1952 Gardner 137-62564 2,624,585 1/ 1953Churchill et a1. 137-62564 XR 2,722,234 11/ 1955 MacGeorge et a1.137-6256 2,916,051 12/1959 Taylor 137-625 .64 2,949,131 8/1960 Collins137-62564 2,993,511 7/1961 Johnson l37625.64 3,263,702 8/1966 Pullen eta1. 137-62564 3,283,784 11/ 1966 Ruchser 137-62564 FOREIGN PATENTS615,008 1/ 1961 Italy.

693,271 8/ 1964 Canada.

955,396 4/1964 Great Britain. 1,190,869 1/ 1958 France. 1,195,115 6/1965Germany.

'M. CARY NELSON, Primary Examiner.

R. I. MILLER, Examiner.

